I also used to meditate and got into a deep meditation one day and started chanting this chant about "the circle be unbroken" which I have since learnt is known in the world of wicca..
I wouldn't be concerned about that. Actually, the common Wiccan phrase is "The circle is open, but unbroken"...in fact, the exact quote "the circle be unbroken" is from the traditional hymn (made famous by the Carter family) "Will the circle be unbroken"...
Will the circle be unbroken
Bye and bye Lord bye and bye
There's a better home a waiting
In the sky Lord in the sky
I wouldn't worry about any demon influence...perhaps subconscious music lyrics??? Circles and such are as much a part of Christian symbolism as Wiccan or other Pagan faiths. Matter of fact, the pentacle (star in a circle) used to be thought of as a symbol of the 5 wounds of Christ...I've seen pics of medieval Cathedrals with pentacle windows. This doesn't mean there were insidious symbols in medieval Catholicism, it just means that symbols can be used by multiple different faiths.
edited because my computer decided to "post" before I typed anything...demons????
edited again because apparently I can't spell! (ok, so I'm anal)